Dear traveller,
If you take a cab at Brussels Zaventem Airport you easily pay 50 to 60 euro for the drive to Brussels. These cabs have the monopoly, and a gentleman had the luminous idea of registrating his cabs in … Flanders (Zaventem) allowing his drivers to charge double fee once half a mile from the airport: entering Brussels Capital. Returning taxis coming from Brussels cannot take passengers, as it is forbidden and they are seriously fined if they do.
So what’s the solution to pay a fair fare (around 30 euro) to reach the capital? Call +32 23 49 49 49 as soon as you arrive. Ask for the forfait to Brussels, give your name and the Brussels taxi-driver will wait four you near the bookstand or supermarket in the arrival hall (having your name on a piece of cardboard). You’ll join the driver to the garage on the other side of the arrival hall. Don’t worry, it’s safe and not illegal and the Taxi Vert will take you to your destination. I used it several times. Enjoy and have a drink ‘on me’.
And more good news: at night from 11 PM to 6 AM, take the collecto-taxis: 6 euro whatever destination 02 800 3636 (for departure/stops see here)

…passengers, as it is forbidden en they are seriously fined if they do.
And nu the fout vinden !